The various events that occur inside a cell, such as metabolism and signal transduction, are orchestrated at the molecular level. For example, in signal transduction, a cascade of biomolecular interactions is initiated. These interactions include (but are not limited to) phosphorylation, binding and transportation of molecules. The effects of these interactions are often transmitted to the nucleus wherein the gene expression pattern is modified based on the signal. In metabolism (e.g., glycolysis), many enzymatic steps occur in sequence. Moreover, activation of enzymes is often controlled by interaction of the enzymes with other molecules (activators). Thus, these enzymatic steps also involve synchronization in terms of movement of molecules, binding and chemical modification.
A cell contains a large number of macromolecules (proteins, nucleic acids, polysaccharides), small molecules (glucose), ions and water. A cell also contains a network of protein filaments, referred to as the cytoskeleton, which is involved in a number of cell processes, in addition to providing mechanical support and defining the structure of the cell. The cytoskeleton is formed from protein filaments (e.g., actin). It can be appreciated that accommodating all these materials in a small volume results in a crowded environment within the cell. Moreover, the protein filaments create confined volumes (or compartments) inside the cell.
In order to study the transportation of molecules inside the cell and organelles such as mitochondria, fluorescent-based experiments have been performed. In these experiments, fluorescent probes (e.g., dextrans or ficolls) are micro-injected into the cytoplasm and the diffusion is studied by measuring the time taken for recovery of fluorescence after photo-bleaching a small area. These experiments reveal that for non-interacting probes (e.g., dextran), transportation is progressively diminished as the molecular weight of the probe is increased. Based on these observations, researchers describe the environment inside the cytoplasm to be “sieving.” This effect is thought to be largely caused by the structure of the cytoskeleton. For probes or molecules that can interact with biomolecules inside the cytoplasm (e.g., DNA), the mobility is more complex. The interaction with molecules leads to “traps” whose strength is related to the specificity of the interaction; i.e., stronger interaction leads to bigger traps. These traps or barriers result in anomalies in diffusion that have been observed both in cytoplasm and in organelles. Moreover, when the cell is depleted of Adenosine Triphoshate (ATP), the mobility of glycolytic enzyme is reduced; thus suggesting that mobility of molecules is affected by the metabolic state of the cell. A common observation of the cytoplasm environment is that the degree of crowding is not consistent. Diffusion of non-interacting probes indicates that certain regions are densely packed compared to other regions. Furthermore, it has been reported that the density of actin filaments (part of the cytoskeleton) is dynamic.
Currently, most biochemical interactions are studied in solution phase wherein the concentration of the molecules is dilute. Given the complexity of the cellular environment, comparing results from dilute solution studies to the actual interactions inside the cell is difficult. For example, side effects of drugs that are designed to interact with specific biomolecules in solution phase may be a result of variations in interaction due to the different environment in the cell. On the other extreme, studies performed inside cells are often difficult to characterize due to multiplicity of interactions and variations between cells. Therefore, there exists a need for a model environment that is simpler than cells yet captures the basic characteristics of the cellular nano-environment such as the presence of charge, crowding, water content and structure. It can be appreciated that such a model environment would aid in the development of effective inhibitory molecules (e.g., drugs) and in understanding the basic mechanisms of cell signaling and behavior.
Therefore, it is a primary object and feature of the present invention to provide a microfluidic-based cell mimic platform for biomolecular studies and a method of mimicking the environment within a cell utilizing the same.
It is a further object and feature of the present invention to provide a microfluidic-based cell mimic platform and a method of mimicking the environment within a cell utilizing the same that more accurately predicts in vivo interactions via in vitro experiments than prior platforms and methods.
It is a still further object and feature of the present invention to provide a microfluidic-based cell mimic platform and a method of mimicking the environment within a cell utilizing the same that are simple and that easily capture the basic characteristics of the cellular nano-environment.
In accordance with the present invention, a platform is provided for mimicking the environment within a cell. The platform includes a microfluidic device defining a chamber and a first hydrogel post is positioned within the chamber. The first hydrogel post defines a first pore therein. A biomolecule is received in the first pore in the post.
The platform may also include a second hydrogel post within the chamber of the microfluidic device. The second hydrogel post includes a second polymer chain defining a second pore. The first pore has a first cross sectional area and the second pore has a second cross sectional area. The second cross sectional area is less than the first cross sectional area. Alternatively, the first hydrogel post may include the second pore having the second cross sectional area. The first hydrogel post may be one of an array of hydrogel posts with the chamber of the microfluidic device. Each hydrogel post of the array of hydrogel posts has a pore therein.
The first hydrogel post is formed from a plurality of cross-linked polymer chains. In addition, a crowding agent may be received in the first pore of the first hydrogel post. The crowding agent is formed from a soluble material captured in the first hydrogel post. The platform may also include a flow of reagent flowing through the chamber of the microfluidic device. The reagent interacts with the biomolecule in the first pore.
In accordance with a further aspect of the present invention, a method is provided for mimicking a nano-environment within a cell to study the interaction between molecules. The method includes the steps of providing a micro device that defines a chamber therein and positioning a first hydrogel post within the chamber of the micro device. The first hydrogel post defines a first pore therein. First and second molecules are deposited in the first pore in the first hydrogel post. Thereafter, the interaction of the first and second molecules in the first pore is observed.
The step of depositing the first molecule in the first pore in the first hydrogel post includes the step of introducing a stream of fluid having the first molecule into the chamber. The first molecule is allowed to diffuse into the first pore. It is contemplated to vary the volume of the first pore. The method includes the additional steps of fabricating the first hydrogel post from a monomer, a cross-linker and a photo-initiator and positioning a second hydrogel post within the chamber of the micro device. The second hydrogel post defines a second pore therein. In a first embodiment, the first pore has a first volume and the second pore has a second volume wherein the second volume is less than the first volume. Alternatively, the first hydrogel post defines the second pore wherein the first pore has a first volume and the second pore has a second volume. The second volume is less than the first volume. In a still further embodiment, the first hydrogel post may be one of an array of hydrogel posts in the chamber.
In accordance with a still further aspect of the present invention, a method is provided of mimicking the environment within a cell. The method includes the steps of providing a chamber and positioning a first post within the chamber. The first post defines a first pore therein. First and second molecules are deposited in the first pore. Thereafter, the interaction of the first and second molecules in the first pore are monitored.
The step of depositing the first molecule in the first pore in the first post includes the step of introducing a stream of fluid having the first molecule into the chamber. The first molecule is allowed to diffuse into the first pore. The step of depositing the second molecule in the first pore in the first post includes the step of introducing a second stream of fluid having the second molecule into the chamber. The second molecule is allowed to diffuse into the first pore. It is contemplated to vary the volume of the first pore. The method includes the additional steps of fabricating the first post from a monomer, a cross-linker and a photo-initiator and positioning a second post within the chamber of the micro device. The second post defines a second pore therein. In a first embodiment, the first pore has a first volume and the second pore has a second volume wherein the second volume is less than the first volume. Alternatively, the first post defines the second pore wherein the first pore has a first volume and the second pore has a second volume. The second volume is less than the first volume. In a still further embodiment, the first post may be one of an array of posts in the chamber.